Semiconductor wafers are normally cut at least 500 μm to 625 μm in thickness because this is considered the minimum thickness necessary to provide structural integrity during integrated circuit wafer processing. Thinner wafers usually break during processing, at which point processing of the wafer usually stops because it is not cost effective to process wafer pieces of irregular shape in a production line. For microwave frequency integrated circuit devices (usually circuits operable in the gigahertz frequency range such as Monolithic Microwave Integrated Circuits or MMIC's), the standard wafer thickness (e.g. 600 μm) is however too thick and thereby excessive device performance losses will occur. Therefore, in microwave circuits, the wafer should be thinned from its backside (the back of the wafer opposite of where the device/circuit is made) in order to reduce circuit inductance and device inductance and minimize radio frequency energy losses. Such wafers are usually thinned to 100 micrometers or even thinner, and require special handling during the backside operation and possibly during subsequent packaging, since the thinned wafers are so structurally weakened as to be quite fragile and unsound. Wafers thinned to as little as 25 to 50 micrometers of thickness have been suggested; such wafers are especially considered to be candidates for use of the present invention.
Normal present day thin wafer backside processing first requires mounting the wafer in a front side (device side) down position onto a wafer carrier (usually of quartz) using wax, and then the backside (with the carrier) can be processed as needed to thin the wafer to its desired thickness. This backside processing usually includes a plurality of grinding and polishing steps and may involve wet processing. This backside processing may also include the provision of via holes to allow a metal connection between the backside and the front side circuits (through the via hole). Once these backside steps have been completed, the wafer is then carefully dismounted from the carrier to make the device front side accessible again. This dismounting procedure is undesirably critical, and frequently results in wafer breakage, as the wafer is now very thin and has become structurally unsound. Furthermore, complete removal of the wax used to mount the wafer front side to the carrier is needed and this removal must be accomplished so as to not damage the devices where the wax was present.